//krazy:exclude=copyright (email of Maxim is missing)
/*
    This file is a part of the KDE project

    SPDX-FileCopyrightText: 2006 Zack Rusin <zack@kde.org>
    SPDX-FileCopyrightText: 2006-2007, 2008 Fredrik Höglund <fredrik@kde.org>

    The stack blur algorithm was invented by Mario Klingemann <mario@quasimondo.com>

    This implementation is based on the version in Anti-Grain Geometry Version 2.4,
    SPDX-FileCopyrightText: 2002-2005 Maxim Shemanarev <http://www.antigrain.com>

    SPDX-License-Identifier: BSD-2-Clause
*/

#include "imagefilter.h"

#include <QPainter>
#include <QImage>
#include <QColor>

#include <cmath>
#include <string.h>

static const quint32 stack_blur8_mul[255] =
{
    512,512,456,512,328,456,335,512,405,328,271,456,388,335,292,512,
    454,405,364,328,298,271,496,456,420,388,360,335,312,292,273,512,
    482,454,428,405,383,364,345,328,312,298,284,271,259,496,475,456,
    437,420,404,388,374,360,347,335,323,312,302,292,282,273,265,512,
    497,482,468,454,441,428,417,405,394,383,373,364,354,345,337,328,
    320,312,305,298,291,284,278,271,265,259,507,496,485,475,465,456,
    446,437,428,420,412,404,396,388,381,374,367,360,354,347,341,335,
    329,323,318,312,307,302,297,292,287,282,278,273,269,265,261,512,
    505,497,489,482,475,468,461,454,447,441,435,428,422,417,411,405,
    399,394,389,383,378,373,368,364,359,354,350,345,341,337,332,328,
    324,320,316,312,309,305,301,298,294,291,287,284,281,278,274,271,
    268,265,262,259,257,507,501,496,491,485,480,475,470,465,460,456,
    451,446,442,437,433,428,424,420,416,412,408,404,400,396,392,388,
    385,381,377,374,370,367,363,360,357,354,350,347,344,341,338,335,
    332,329,326,323,320,318,315,312,310,307,304,302,299,297,294,292,
    289,287,285,282,280,278,275,273,271,269,267,265,263,261,259
};

static const quint32 stack_blur8_shr[255] =
{
    9, 11, 12, 13, 13, 14, 14, 15, 15, 15, 15, 16, 16, 16, 16, 17,
    17, 17, 17, 17, 17, 17, 18, 18, 18, 18, 18, 18, 18, 18, 18, 19,
    19, 19, 19, 19, 19, 19, 19, 19, 19, 19, 19, 19, 19, 20, 20, 20,
    20, 20, 20, 20, 20, 20, 20, 20, 20, 20, 20, 20, 20, 20, 20, 21,
    21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21,
    21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 22, 22, 22, 22, 22, 22,
    22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22,
    22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 23,
    23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23,
    23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23,
    23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23,
    23, 23, 23, 23, 23, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24,
    24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24,
    24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24,
    24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24,
    24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24
};

inline static void blurHorizontal(QImage &image, unsigned int *stack, int div, int radius)
{
    int stackindex;
    int stackstart;

    quint32 * const pixels = reinterpret_cast<quint32 *>(image.bits());
    quint32 pixel;

    int w = image.width();
    int h = image.height();
    int wm = w - 1;

    unsigned int mul_sum = stack_blur8_mul[radius];
    unsigned int shr_sum = stack_blur8_shr[radius];

    unsigned int sum, sum_in, sum_out;

    for (int y = 0; y < h; y++)
    {
        sum     = 0;
        sum_in  = 0;
        sum_out = 0;

        const int yw = y * w;
        pixel = pixels[yw];
        for (int i = 0; i <= radius; i++)
        {
            stack[i] = qAlpha(pixel);

            sum += stack[i] * (i + 1);
            sum_out += stack[i];
        }

        for (int i = 1; i <= radius; i++)
        {
            pixel = pixels[yw + qMin(i, wm)];

            unsigned int *stackpix = &stack[i + radius];
            *stackpix = qAlpha(pixel);

            sum    += *stackpix * (radius + 1 - i);
            sum_in += *stackpix;
        }

        stackindex = radius;
        for (int x = 0, i = yw; x < w; x++)
        {
            pixels[i++] = (((sum * mul_sum) >> shr_sum) << 24) & 0xff000000;

            sum -= sum_out;

            stackstart = stackindex + div - radius;
            if (stackstart >= div)
                stackstart -= div;

            unsigned int *stackpix = &stack[stackstart];

            sum_out -= *stackpix;

            pixel = pixels[yw + qMin(x + radius + 1, wm)];

            *stackpix = qAlpha(pixel);

            sum_in += *stackpix;
            sum    += sum_in;

            if (++stackindex >= div)
                stackindex = 0;

            stackpix = &stack[stackindex];

            sum_out += *stackpix;
            sum_in  -= *stackpix;
        } // for (x = 0, ...)
    } // for (y = 0, ...)
}

inline static void blurVertical(QImage &image, unsigned int *stack, int div, int radius)
{
    int stackindex;
    int stackstart;

    quint32 * const pixels = reinterpret_cast<quint32 *>(image.bits());
    quint32 pixel;

    int w = image.width();
    int h = image.height();
    int hm = h - 1;

    int mul_sum = stack_blur8_mul[radius];
    int shr_sum = stack_blur8_shr[radius];

    unsigned int sum, sum_in, sum_out;

    for (int x = 0; x < w; x++)
    {
        sum     = 0;
        sum_in  = 0;
        sum_out = 0;

        pixel = pixels[x];
        for (int i = 0; i <= radius; i++)
        {
            stack[i] = qAlpha(pixel);

            sum += stack[i] * (i + 1);
            sum_out += stack[i];
        }

        for (int i = 1; i <= radius; i++)
        {
            pixel = pixels[qMin(i, hm) * w + x];

            unsigned int *stackpix = &stack[i + radius];
            *stackpix = qAlpha(pixel);

            sum    += *stackpix * (radius + 1 - i);
            sum_in += *stackpix;
        }

        stackindex = radius;
        for (int y = 0, i = x; y < h; y++, i += w)
        {
            pixels[i] = (((sum * mul_sum) >> shr_sum) << 24) & 0xff000000;

            sum -= sum_out;

            stackstart = stackindex + div - radius;
            if (stackstart >= div)
                stackstart -= div;

            unsigned int *stackpix = &stack[stackstart];

            sum_out -= *stackpix;

            pixel = pixels[qMin(y + radius + 1, hm) * w + x];

            *stackpix = qAlpha(pixel);

            sum_in += *stackpix;
            sum    += sum_in;

            if (++stackindex >= div)
                stackindex = 0;

            stackpix = &stack[stackindex];

            sum_out += *stackpix;
            sum_in  -= *stackpix;
        } // for (y = 0, ...)
    } // for (x = 0, ...)
}

static void stackBlur(QImage &image, float radius)
{
    radius = qRound(radius);

    int div = int(radius * 2) + 1;
    unsigned int *stack  = new unsigned int[div];

    blurHorizontal(image, stack, div, radius);
    blurVertical(image, stack, div, radius);

    delete [] stack;
}

void ImageFilter::shadowBlur(QImage &image, float radius, const QColor &color)
{
    if (radius < 0)
        return;

    if (radius > 0)
        stackBlur(image, radius);

    // Correct the color and opacity of the shadow
    QPainter p(&image);
    p.setCompositionMode(QPainter::CompositionMode_SourceIn);
    p.fillRect(image.rect(), color);
}

// kate: space-indent on; indent-width 4; replace-tabs on;
